In summation, this study will measure the effect of alcohol consumption on changes in bone health prospectively in HIV-infected adults with current substance dependence or ever injection drug use. To our knowledge, no other prospective HIV/bone study has studied these relevant factors simultaneously or used HR-pQCT to assess bone microarchitecture. Data on alcohol risks to bone health is important information for defining risky drinking amounts for people with HIV infection (and for advising such patients accordingly).